It is often desirable to remove sediment and other particulate matter from a waterway such as a stream, river, channel bed, tidal pool, or estuary pool. Sediments are often soils eroded from farmland, forests, and runoff from city streets, carried by surface water, and accumulated in channel bottoms. The sediments are typically sand and silts that have been carried by the waterway or along a lake shoreline by littoral currents and deposited in the deepened channel. A dredged material may be a clean soil or may have contaminants that came from a number of possible sources including urban runoff, sewer overflows, mining, etc.
Whatever the source, sediment removal from a channel bed is often done for a variety of reasons, including removing sediments to improve a spawning area, improving navigation by removing sand bars, removing contaminated sediment from industrial runoff in streams, and removing sediment from aqueduct and generating station intakes.
A common way to remove sediment from streams is by dredging. In conventional mechanical dredging techniques, a crane with a bucket scoops sediment from a bottom surface of the waterway and deposits the sediment in a barge or vehicle for transport to a remote location. While effective, such dredging techniques require expensive equipment and are costly to operate. In addition, conventional “grab type” dredging techniques such as “clamshell bucket” or “drag line bucket” are designed to operate without concern for excess sediment spilling out of the buckets during operation, i.e., sediment is stirred up in the waterway and fouls downstream locations. These dredging techniques commonly produce a flume of waterborne sediments that are widely dispersed by the prevailing currents. Thus, the conventional grab type dredges are not well suited for the retrieval of contaminated marine sediments. On the other hand, hydraulic dredging produce a large volume of associated water, which is usually directed to a settling pond and returned to the waterway after the sediment has settled. When the soil contains contaminated sediments, the associated water must be treated using a remediation process before it is returned to the waterway. This requirement increases the degree of difficulty and cost of a project.
Another alternative to dredging is to use the applicant's collector assembly as shown and described in U.S. Pat. Nos. 6,042,733 and 6,346,199. One or more collectors are mounted in the waterway and sediment that collects in the assembly is periodically pumped on shore. This collector assembly has proven to be especially effective at removing sediment from waterways. Typically, a pump is disposed outside of the waterway and, oftentimes, associated with an ejector to provide suction to a sediment removal passage. The sediment is separated from the water by passing through a filter and clean, filtered water returned to the waterway.
These systems do not adequately address the need for a mobile or portable sediment removal.